The purpose of this study is to morphologically identify the mechanism by which lysosomal enzymes are secreted and taken up by human fibroblasts. Ultrastructural cytochemistry has been used to identify lysosomes and a network of lysosomal enzymes, called GERL. Various parameters including culture conditions, transformation, and lysosomotropic drugs will be studied for their effects on lysosomal and GERL formation. In addition, localization of the surface receptors of lysosomes will be attempted by means of antibody techniques.